Stringed musical instrument



Dec. Z6, 1961 G. F. BLAIR 3,014,395

STRINGED MUSICAL INSTRUMENT Filed March 25, 1958 2 Sheets-Sheet 1 12 j! .I4 Mj.

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INVENTOR.

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4free/ogg Dec. 26, 1961 G. F. B| A1R 3,014,395

STRINGED MUSICAL INSTRUMENT Filed March 25, 1958 2 Sheets-Sheet 2 @E0/QSE .FZ gan/A2,

INVENTOR.

BYMW'M Patented Dec. 26, 1961 3,014,395 STRINGED MUSICAL INSTRUMENT George F. Blair, 13828 S. Jersey Ave., Norwalk, Calif. Filed Mar. 25, 1958, Ser. No. 723,710 1 Claim. (Cl. 84--312) The present invention relates to an improvement in a stringed musical instrument, and more particularly to an improved mechanism for varying the tension and consequently the vibration frequency of one of the strings of the instrument.

In stringed musical instruments it is conventional to support each string upon a pair of fixed supports having a fixed distance therebetween, thus establishing the length of the string which is to be permitted to vibrate for producing a musical tone. lt is also conventional to utilize a rigid fastening for one end of the string, and to Ahave the other end of the string pass over a rigid support to an adjustable tuning knob, so that the string tension can be adjusted from time to time to provide the desired vibration frequency for the particular string.

When the basic tuning of the string has been adjusted by adjusting the tuning knob, frequent readjustment may nevertheless be required. For example, Where a musicianis playing before a large audience the room temperature tends to rise during the performance, requiring readjustment of the tuning knob in order to maintain the desired vibration frequency for the particular string.

In certain instruments such as guitars the musical pitch for each string is also controlled by utilizing a movable support in order to select lessl than all of the distance between the two fixed supports as the vibrating portion of the string. Thus, a. backboard is positioned parallel to the string near'one of the fixed supports, and a movable v f) member such as a piece of steel 1s placed upon the string to depress it against the backboard, the length of the vibrating string then being the distance between the movable member and the other fixed support.

As an alternative to changing the length of the string in order to control its vibrating frequency 4it is possible to change the string tension. Devices for this purpose are conventionally used in the steel guitar, and known either as a chord changer or as a tuning changer, depending upon the characteristics of the particular device. A so-called chord changer is a device capable of changing the reference vibration frequency, and consequently the reference pitch, of a particular string of the instrument, and thus changing the musical nature of a chord which may be produced by using that particular string in conjunction with one or more of the other strings. A so-called tuning changer is a device which is capable of changing the reference pitch of all of the strings at one time, thus making it appear that a different instrument has been substi tuted for the original one. A device of either type must also be capable of restoring the string or strings to their respective initial vibration frequencies.

The present invention provides an improved tuning changer consisting of a plurality of individual units, one for each string of the instrument. By using only one such unit a chord changer can, obviously, be provided. The invention is therefore described primarily with reference to a single string of the instrument, and the tuning mechalnism associated therewith.

Previously known chord changers and tuning changers have been subject to the difficulty that once the reference pitch of the particular string has been changed, when the device is operated a second time in order to restore the string to its initial vibrating frequency, the precise musical pitch previously produced by the string cannot again be attained. ln other words, assuming that the device can be adjusted and manipulated so as to change the string from condition X to condition Y, the inherent mechanical lag of the device is usually such that -it is then impossible to return the string precisely to the X condition. It is essential that such a device ybe able to control the string tension within a fraction of 1% since otherwise the discrepancy in musical pitch will be of unpermissable magnitude. In fact, it is probable that skilled musicians can detect discrepancies in vibrating frequency of the order of 0.01%, or one part in ten thousand, hence such a degree of precision is necessary for a high-quality instrument.

An object of the invention, therefore, is to provide an improved device for varying the tension in a string of a stringed musical instrument in a controllable fashion, and for reliably causing the string tension to return to its precise initial value afterthe controlled variation has been completed.

Another object of the invention is to provide an improved device for use in a steel guitar, for controllably increasing or decreasing the tension of a taut string.

Yet another object of the invention is to provide an improved stringed instrument including a mechanism supporting one end of the vibrating portion of the string and adapted to reliably and precisely control the vibrating frequency of the string by varying the string tension.

The above and other objects of the invention will be more readily understood from the following description in conjunction with the accompanying drawings, in which:

FIGURE l is a perspective view of a steel guitar ernbodying a tuning changer as provided by the present invention;

FlGURE 2 is an enlarged partial longitudinal sectional view of the guitar of FIGURE l taken along line 2 2 thereof and illustrating the tuning changer mechanism;

FIGURE 3 is an end elevational view of the tuning changer mechanism taken along line 3-3 of FlGURE 2;

FIGURE 4 is an exploded partial view of one individual unit of the tuning changer;

FIGURE 5 is a side elevational view of a tuning changer unit illustrating how the associated string is tightened;

FlGURE 6 is a side changer unit illustrating loosened;

FIGURE 7 is a horizontal sectional view of one of the tuning changer units illustrating a condition of normal string tension;

FIGURE 8 is a horizontal sectional view of the tuning changer unit shown in FIGURE 5; v

FIGURE 9 is a horizontal sectional View of the tuning changer unit shown in FIGURE 6; and

FIG-URE 10 illustrates a control knob used to actuate the 'tuning changer units.

Reference is now made to the drawings where it may be seen that an instrument A having a frame B has at one end thereof a fret C which constitutes a xed support for a plurality of strings D1-D8. A tuning changer generally designated as 30 and mounted at the other end of the frame contains a number of separate tuning changer units, one for each of the strings, as will be explained.

Strings D1-D8 pass over the fret C and are received by conventional adjusting knobs 11-18, respectively. The tuning adjustment accomplished by means of these knobs is a relatively fixed tuning which is utilized to establish the proper initial conditions, and unlike the invention, does not enter into the actual playing of the instrument. A cover plate 19 is provided to cover this conventional tuning mechanism.

A tone pickup unit 21 is mounted on the frame of the instrument immediately adjacent tuning changer 30, and all of the strings D pass through the pickup unit and are permitted to vibrate freely therein. Pickup unit 21 includes a horizontal base member 22, a pair of vertical end plates 23 which are parallel to each other and to strings elevational view of a tuning how the associated string is L! D, and a horizontal cover plate 24 supported by end plates 23 and which extends over strings D. A plurality of probes 26 extend upwardly from base plate 22, one for each string, in order to pick up and amplify the string vibrations by electrical means, not shown.

A shaft E mounted transversely with respect to the frame supports a rotatable member F in each tuning changer unit. The associated string D passes over the surface of rotatable member F and has its end firmly fastened to a fastening device G. Rotatable member F has a circular bore 42l which receives shaft E in relatively snug engagement. Member F may be cut or stamped from a plate of suitable thickness so as to provide its string-supporting surface 42 with a width at least twice the string thickness. The upwardly extending portion of member F as shown in the drawings is arcuate and is concentric to bore 41, thus providing a surface portion 43 which constitutes a semi-cylindrical surface. At one end of the semi-cylindrical surface 43 the string-supporting surface 42 extends outward and downward to form a lip 44 which terminates at a position which is below and to the left of bore 41, at an angle of about 45 from the horizontal, and almost twice as far from bore 41 as is the semi-cylindrical surface 43. Lip 44 is preferably dished near its extremity to provide a secure position for the String and has an undercut portion G adapted to receive in secure engagement a member G to which the end of the taut string D is fastened.

Each string D is therefore supported at one of its ends upon fret C which provides a fixed support, and has the end portion adjacent its other end supported upon rotatable member F, and more particularly, upon lip 44 and a portion of semi-cylindrical surface 43. String D contacts surface 43 tangentially at point 46 so that string D forms a right angle with the vertical line passing through point 46 and the axis of shaft E. Semi-cylindrical surface 43 encompasses a sufficient angular portion of rotatable member F so that for any desired amount of string tension the initial point of contact between string D and rotatable member F falls upon the semi-cylindrical surface. The length of string D which is free to vibrate as a single unit is therefore equal to the distance between fret C and contact point 46, and is substantially independent of variations in the string tension.

Tuning changer 30 is enclosed within a housing which includes a vertical back plate 31, a vertical front plate 32, and a horizontal top plate 33. Frame B, which is preferably made of wood in the conventional manner, has a suitable aperture for seating the tuning changer housing assembly in a rigidly secure position.V

Each tuning changer unit consists primarily of a triplelever arrangement, where rotatable member F is the first lever and there are second levers 50 and 60, respectively. Second lever 50 at its upper end has a circular bore 51 adapted to receive shaft E in snug engagement therewith. Lever 50 is of substantial length and depends downwardly from shaft E. First lever F and second lever Si) are therefore rotatable about a common axis which is fixedly positioned with respect to the frame of the instrument, namely, the longitudinal axis of shaft E.

Rotatable member F has a downwardly depending tail portion 45 whose extremity is engaged by lever 60, so that rotatable member F itself operates as a lever. The length of lever F from its lower end to the center of bore 4l is substantially greater than the radius of curvature of semi-cylindrical surface 43, hence lever F provides a positive mechanical advantage in manipulating the tension of string D.

A substantial distance below circular bore 51 lever 50 is provided with an additional circular bore 52 for receiving an auxiliary shaft 53. As will be seen in FEGURE 3 there is a separate auxiliary shaft 53 for each of the eight tuning changer units. The function of auxiliary shaft 53 is to interconnect second lever 50 and third lever 60, and it is not directly connected either to the frame of the instrument or to the tuning changer housing. Lever 60 depends downwardly and provides substantially a vertical extension of lever F. Lever 60 has near its upper end a circular bore 61 adapted to receive axuiliary shaft 53 in snug rotatable engagement therewith. Third lever 60 is therefore adapted to rotate about a second axis which is substantially removed from said common axis, namely, the longitudinal axis of auxiliary shaft 53 which is supported from circular bore S2 of lever 50. First lever F and second lever 50 are adapted to rotate with respect to the frame of the instrument in adjacent parallel planes, while third lever 60 is adapted to rotate in the same plane of rotation as first lever F.

Lever at? has at its upper end, above bore 61, a laterally extending portion 62 which overhangs a front edge portion 54 of lever S0 intermediate to bores 51 and 52 thereof. Overhanging portion 62 of lever 60 therefore serves to limit the clockwise rotation of third lever 60 relative to second lever 50. Overhanging portion 62 carries a transversely extending shaft 63 (which may be a rivet mounted in a suitable hole) and rotatably supporting a roller 64 which provides the upper extension of lever 60. Roller 64 engages the front surface of downwardly depending tail 45 of lever F. Thus any clockwise rotation of third lever 60 produces a counterclockwise rotation of lever F, but the tension of string D tends to produce a clockwise rotation of lever F. A retaining spring 66 has one end 65 fastened to back plate 31 and the other end 67 fastened to the lower end of lever 60. The force applied by spring 66 tends to produce clockwise rotation of lever 5t?, and, because of the very substantial mechanical advantage of lever 60, is capable of overcoming the force from string D tending to produce rotation in the opposite direction (that is, clockwise for lever F and counterclockwise for lever 60). Because of the c0nnection of lever 60 to lever 5t) via auxiliary shaft 53 the string tension also tends to produce a clockwise rotation of lever 5d. A substantial distance below auxiliary shaft 53 a fixed stop 55 supported by the tuning changer housengages a front surface portion 57 of lever 50 and thus limits the clockwise displacement of lever 50.

The housing of tuning changer 30 also includes side plates 35, 36 which interconnect back plate 31 and front plate 3?.. As shown in FIGURES l and 2` a plurality of control knobs 7i) mounted on the Surface 0f side plate 35 control the angular positions of a corresponding plurality of shafts 71a, '71b, 71C, 71d which extend horizontally through the tuning changer housing, parallel to shafts E and 53, and at a right angle to levers 50 and 60 and immediately adjacent thereto. Each shaft 71a-71d has at least one transverse threaded bore 75 which receives a threaded adjustment pin such as pin 55 supported by shaft 71]; (FIGURE 2) or pin 76 supported `by Shaft 71a (FIG- URE 5). As shown in FIGURE l0 each control knob 70 may be provided with a stop 80 which limits its angular motion to providing one position in which a corresponding pin mounted on the associated shaft is parallel to levers 50 and 60, and another position in which it is at a right angle to levers 50 and 60.

The operation of my invention is carried out as follows. The string end is fastened to member G which is then Seated in seat G of lever F, and the string tightly wrapped around lip surface 44 and a portion of semi-cylindrical surface 43 of lever F. The other end of the string is passed over fret C and fastened to the corresponding one of tuning knobs 11-18, which is utilized to establish the proper string tension. Shaft 71b is maintained in such position that adjustment pin 55 provides a fixed stop which limits the clockwise rotation of lever 50. As shown in FIGURE 7 stop 55 limits the motion of lever 50 but not of lever 6th When it is desired to tighten the string tension and thus raise its vibrating pitch the procedure is as follows. Shaft 71a is rotated to bring its adjustment pin '76 into Contact with the downwardly depending shank of second lever 50 (FIGURES 2 5 and 8). Pin '76 contacts lever 50 but not lever 60. The adjustment of pin 76 is such as to produce a dellection of lever 50, and a counterclockwise rotation relative to its normal :or static position established by pin 55. Counterclockwise rotation of secon-d lever 50 acts upon third lever 69 and hence upon first lever F to produce a corresponding counterclockwise rotation of iirst lever F. rThis tightens the string and raises its musical pitch.

When it is desired to lower the pitch of the string the procedure is as follows. Shaft 71a` is rotated to depress lever 6d (see FIGURES 2, 6 and 9). Adjustment pin 77 supported on shaft 71e engages lever 60 but not lever 50 (see FIGURE 9). Pin 77 is adjusted so as to engage lever 60 and produce counterclockwise rotation thereof. Counterclockwise rotation of third lever 60 relative to second lever 50 permits a clockwise rotation of rst lever F relative to the frame of the instrument, and the tension of string D is accordingly loosened and its musical pitch is lowered.

Precision control of the string tension depends to a large extent upon the interaction of the upper end of third lever 6) and the lower end of irst lever F. According t0 a preferred form of lever F which is shown only in FIG- URE 6, downwardly depending tail 45 thereof has a bevel-led surface 48 which is normally inclined at an angle of approximately 45. Roller 64 constituting the upper end of third lever 60 normally engages the extreme upper end of bevelled surface 48. When the string tension is tightened by rotating lever 50 in a counterclockwise direction levers 60 and F rotate in exact synchronism with lever 50, and there is no relative motion between roller 64 and bevelled surface 48. On the other hand, when string tension is lto beloosened and lever 60 is rotated counterclockwise, lever F rotates'cl'ockwise and roller 6,4 rolls down bevelled surface 48'toward the lower end thereof. "Actual experimentation has demonstrated the value of the particular shape of lever F as illustrated. More specifically, although in theory it might seem that lever F should be a cylindrical member having a lever handle 45 appended thereto, experience has shown that lip 44 has great practical utility and improves the convenience and the reliability of the device.

Because of the extended contact between string D and the surface of lever F, the vibration of the string induces vibration in the tuning changer mechanism. This c0- operative action is particularly useful in improving the quality of bass notes.

Although my invention is fully capable of achieving the results and providing the advantages hereinbefore mentioned, it is to be understood that it is merely the presently preferred embodiment thereof, land that I do not mean to be limited to the details of construction above described other than as delined in the appended claim.

l claim:

in a stringed musical instrument having a frame, apparatus for bilaterally adjusting the tension of a taut string, comprising in combination: a lever member supported from the instrument frame for rotation about a iixed axis, said lever member having a semi-cylindrical surface concentric with said fixed axis and a curved surface contiguous with said semi-cylindrical surface which extends in the direction of increasing radius with respect to said iixed axis, and including a lever arm projecting perpendicular to said iixed axis; means fastening the otherwise free end of the string to said lever member adjacent the outer end of said curved surface for supporting the string upon said semi-cylindrical surface perpendicular to said fixed axis; and means cooperating with said lever arm of said lever member for rotating said lever member so as to selectively loosen or tighten the string, said last named means including a pair of biased levers each provided with motion-limiting means, together with means for selectively actuating one or the other of said pair of levers.

References Cited in the le of this patent UNITED STATES PATENTS Ferriera July 29, 1958 

